The invention relates to a device for changing control times for gas-exchange valves in an internal combustion engine according to features recited in the preamble of claim 1, which can be realized especially advantageously on a rotary piston adjustment device for angular adjustment of a camshaft relative to a crankshaft.
From DE 101 50 856 A1, a class-defining device for changing control times of gas-exchange valves in an internal combustion engine is known, which is mounted on the drive end of a camshaft supported in the cylinder head of an internal combustion engine and which, in principle, is embodied as a hydraulic actuator that can be controlled as a function of various operating parameters of the internal combustion engine. This device essentially consists of a drive wheel, in driven connection with the crankshaft of the internal combustion engine, and of a vane rotor, which is locked in rotation with the camshaft of the internal combustion engine. The drive wheel and vane rotor are in force-transmitting connection with each other and transmit the torque of the crankshaft to the camshaft of the internal combustion engine. The drive wheel has a hollow space, which is formed by a hollow cylindrical peripheral wall and two lateral walls and in which five hydraulic work chambers are formed by five radial limit walls which extend towards the longitudinal center axis of the device. Correspondingly, on the periphery of its rotor hub, the vane rotor has five vanes, which extend radially into the work chambers and which sub-divide the work chambers into an A pressure chamber and a B pressure chamber, which can be used to cause a pivoting motion or to fix the vane rotor relative to the drive wheel and thus the camshaft relative to the crankshaft through selective or simultaneous pressurization with a hydraulic pressure medium. In addition, the vane rotor can be mechanically coupled to the drive wheel by a separate locking element in a preferred base position within its adjustment region when the pressure medium pressure falls below a pressure necessary for adjustment, such as, for example, when the internal combustion engine is turned off, in order to prevent rattling of the vane rotor striking the limit walls of the drive wheel due to the changing torque of the camshaft, especially when the internal combustion engine is restarted and until the necessary pressure medium pressure has been established. This locking element, embodied as a sleeve-like cylinder pin, is arranged in a continuous axial bore hole in the rotor hub of the vane rotor and can move into a locked position within a receptacle in the lateral wall of the drive wheel facing away from the camshaft by a spring element, which is provided as a compression coil spring and which is supported on one side on the rear side of the locking element and on the other side on a holder similarly inserted into the axial bore hole. The receptacle of the locking element is connected to one of the A pressure chambers of the device via a pressure medium supply groove machined into the inner surface of the lateral wall facing away from the camshaft, so that when the A pressure chambers have been pressurized, the locking element can move hydraulically into an unlocked position within the axial bore hole in the rotor hub of the vane rotor.
However, a disadvantage in this known device is that the locking element is in constant pressure medium connection with the corresponding A pressure chamber of the device for mechanical coupling of the vane rotor with the drive wheel in its unlocked position also outside of the base position of the vane rotor via the pressure medium supply groove to its receptacle in the lateral wall of the drive wheel, so that when the A pressure chambers are pressurized, the applied pressure medium pressure and also the resulting pressure peaks of the pressure medium also act permanently on the locking element or on the entire locking mechanism. Because the pressurized locking element is supported on its holder arranged in the axial bore hole of the rotor hub and the usually plastic holder is supported on its side on the lateral wall of the drive wheel facing the camshaft and closing the axial bore hole, the pressure medium pressure permanently acting on the locking element leads to increased wear on the holder and on the lateral wall of the drive wheel due to the constant relative rotation between the vane rotor and the drive wheel. However, this wear negatively affects the function of the locking mechanism in a disadvantageous way and can lead to a loss of function over the service life of the device.